I am conducting the linear mixed effects analysis by SPSS. I have few questions and highly appreciate your help:

1- How can I compare two linear mixed effects models to find the best model?
I've been told to use the t-test for coefficients but how? What is the SPSS command?

I need to compare one simple mixed effects model with the Univariate one.

2- How can I obtain the fitted values for my model?

3- How can I plot my mixed effects model in a way that it also shows confidence interval. I plotted the predicted value versus my independent variable but it looks like the linear line and it does not show me the confidence interval.